1190 A novel ‘2+1’bispecific T cell engager platform, enables enhanced anti-tumor activity with reduced risk of CRS

Background

CD3 T cell engaging bispecific antibodies (TCE) redirect T cells to attack targeted tumor cells by simultaneously binding TAA on cancer cells and CD3 complex on a T-cell to form a TCR-independent immune synapse. Multiple TCEs have demonstrated promising therapeutic efficacy in the treatment of hematological malignancies, whereas suboptimal efficacy in the treatment of solid tumors and the risk of inducing cytokine release syndrome (CRS) continue to be major challenges. Several factors, such as format, affinity, and valency of the antibody, TAA copy number, antigen size and epitope can impact therapeutic efficacy and safety of a TCE. In this study, we developed a novel ‘2+1’ TCE platform, AnTenGager^TM, which enables potent anti-tumor activity with reduced risk of CRS.

Methods

Humanized CD3 antibodies was derived from mouse hybridoma, followed by affinity optimization utilizing Computer Aided Drug Design (CADD). Fab-scFv-Fab format was used as the backbone structure of AnTenGager^TM. The anti-CD3 scFv sequences and the length of peptide linkers between VH/VL, scFv/CH1, and scFv/CH2 were screened and compared in a variety of preclinical assays. LALA mutations (L234A, L235A) were introduced to abolish the Fc receptor binding capability. In a series of in vitro and/or in vivo models, the efficacy and safety of AnTenGagers targeting multiple TAAs, such as Her2, GD2, CD20, LILRB4, and GPRC5D, were evaluated.

Results

We generated a library of humanized parental CD3 antibodies with a broad spectrum of affinities, some of which cross react with monkey CD3. AnTenGagers exhibited limited binding to CD3-positive cells without TAA-crosslinking, suggesting reduced risk of CRS caused by systemic CD3 activation. For instance, four CD3 sequences with varying affinities were utilized to construct AnTenGagers with the same TAA-targeting arm. Compared to clinical benchmarks targeting the same TAA, all four AnTenGagers demonstrated substantially lower binding capacity to CD3+ cells without TAA-crosslinking, while inducing increased cytotoxicity against target-positive tumor cells (figure 1). In addition, they induced significantly less ex-vivo cytokine release by human PBMC than benchmarks. Notably, four AnTenGagers demonstrated enhanced in vivo efficacy compared to the benchmark, exhibiting complete response (CR) in PBMC humanized mouse tumor model. The serum concentration of proinflammatory cytokines was substantially lower in groups treated with AnTenGagers (figure 2).

Conclusions

These results suggested that AnTenGager is promising platform to develop the next generation of TCEs with improved efficacy and safety profiles.

Ethics Approval

Crownbio: 001243